ATOP MAUNA KEA, Hawaii - If you count from sea level, we were 13,796 feet up, almost as high as Mount Rainier. Plenty high enough.

But if you count from the ocean floor? My Big Island tour group was shivering in thin air atop the Earth's highest mountain - 33,500 feet from its waterlogged base to pumice-laden peak.

And that measure seemed the more meaningful, because this place seemed to have far more to do with outer space than with anything terrestrial.

As the sunset painted clouds tropical hues of mango and papaya - this was still Hawaii, after all - the nightly crowd of parka-clad, camera-snapping tourists looked like so many geckos swarming around a dozen enormous observatories dotting the top of Hawaii's highest peak.

Amid tomato-red cinder cones, about the only thing that grows is the rare silver sword plant. The big crop atop Mauna Kea is telescopes, including the world's two largest functional telescopes, with mirrors 33 feet across, at the W.M. Keck Observatory. (By way of comparison, the Hubble Space Telescope comes in at a measly 8 feet.)

Being here is much more than a chance to see a pretty sunset - though those can be amazing. It's a bit like going to Cape Canaveral for a rocket launch. Every visitor to the summit of this dormant volcano is giddy, and not just from thin air.

Hundreds of scientists and engineers support the Mauna Kea observatories, while data from the telescopes are transmitted worldwide to astronomers. One night's use of a Keck telescope is valued at $50,000.

The Keck Observatory alone is credited with detecting more planets outside our solar system than any other observation post, and helped in discovery of the accelerating expansion of the universe, for which astronomers earned the 2011 Nobel Prize in physics. Just seeing this place makes you feel smarter.

Other observatories at the top represent partners such as NASA, the Smithsonian, governments from Japan to the United Kingdom, and universities such as Cal Tech.

The high altitude - above 40 percent of the Earth's atmosphere - along with dark skies and dry, clean air attracted astronomers to Mauna Kea starting in 1964 when the state of Hawaii spent $42,000 to build the cliff-climbing road, the third highest in the United States

"Usually it's so dry up here you can't see your breath in the cold!" Brown told our group as our van headed up like a plane taking off.

One interpretation of Mauna Kea's name is "white mountain," since it's the only place in Hawaii to regularly get winter snow. "Here you'll see the only example of snow-removal equipment in the state of Hawaii!" Brown quipped as we drove past a road-crew barn.

But snow clouds, or any clouds, don't often cover the summit. The proportion of clear nights is among the highest in the world, and astronomers continue to pledge their allegiance to Mauna Kea: The next big thing coming here is the Thirty Meter Telescope, three times larger than any on Earth, so powerful that it will bring in to view galaxies forming at the edge of the observable universe, near the beginning of time. (Chew on that along with your macadamia-nut fudge.)

Construction may begin by year's end at a cost of up to $1.2 billion. Backers include Japan, India, China and universities across Canada and California.

Visiting Mauna Kea is a special thrill for science buffs, but don't expect to peek through one of the big telescopes (see the price tag, above). And while most tour operators go up for sunset, the few observatories that welcome visitors close at 4 p.m., so unless you go up on your own you won't get inside.

Even in a comfortable tour van specially built for the steep road, it's no drive to the beach. As we climbed, Brown warned us of the hazards of altitude sickness.

"You might be short of breath, you might feel a little dizzy," he warned.

"Yee-ha!" crowed a woman in the rear.

If those symptoms, or headache, are severe, he said, "I have a little bottle of oxygen and I hook you up to Greg's Oxygen Bar and get you down the hill."

To acclimate to the elevation change, we'd stopped for a picnic dinner in cypress woods near the 7,000-foot level. Other tour groups and visitors typically stop at the 9,300-foot level at the visitor-information station at the Onizuka Center for International Astronomy, named for Ellison Onizuka, a hometown Kona astronaut who died in the Challenger space shuttle explosion in 1986.

Authorities urge summit visitors to use four-wheel drive vehicles because of the steep, rough road, and to respect the altitude at the summit, where temperatures often get down to freezing. Kids younger than 16 and anybody with health problems are strongly discouraged from going higher than the visitor center.

The cautions don't convince all, though.

"Here's one of those four-wheel drive Mustangs coming down, and this one's a convertible," Brown noted with sarcasm on our way up.

At the summit, we donned parkas provided by our guide. For my early-June visit, the temperature was in the upper 30s, with winds to 20 mph. Fingers quickly numbed. The wind was 83 mph a few days earlier.

The combination of excitement and low oxygen seemed to transform the tour group into giggly schoolkids, gawking at the summit's moonlike landscape dotted with gleaming observatory domes.

I ran to get a photo of the mountain's sunset shadow against clouds below, but quickly stopped when my heart pounded and breath ran short. But just stopping to gaze was rewarding.

"Oh, wow! Look at the clouds, and the clouds above the clouds!" said Shelley Burr, a Boeing employee visiting from Seattle. "You don't have words for this. It's the top of the world!"

After a half-hour of wild photo snapping, Brown called out, "Look, Gemini Northern (observatory) is rotating, and Keck has their doors open!" The observatories were opening for the night. It felt like a sci-fi movie set.

It would be a shame to get up in that clear air and not wait for stars to come out. So we drove back to the visitor center where Brown set up an 11-inch-wide telescope for our own star party, which included both the Northern Star and Southern Cross in one swivel of the head.

On the dark road back to the Kona hotel strip, Brown suddenly braked the van to point out the Big Island's active volcano. "Look, over near the base of Mauna Loa, see that red glow? That's Kilauea!"

Whoa. The glow from lava from the planet's bowels capped off the night, and brought us all back to earth.

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IF YOU GO:

TOURS: I took the Mauna Kea Summit and Stars Adventure ($200, including picnic dinner and one-hour stargazing party) with Hawaii Forest & Trail (800-464-1993 or http://www.hawaii-forest.com ). The 14-passenger van left the town of Kailua-Kona at 3 p.m. and returned around 10:30 p.m., with about 45 minutes to watch sunset at the summit. A guide provided details on natural, cultural and geologic history; fellow passengers agreed it was worth the price.

A sampling of other tour operators:

Mauna Kea Summit Adventures offers a 15 percent discount off the $200 fee for early bookings in off-peak times; 888-322-2366 or http://www.maunakea.com.

Jack's Tours, 800-442-5557 or http://www.jackshawaii.com.

TRAVELER'S TIPS:

-For the best stargazing, plan to visit on a night with little or no moon visible.

-It is possible to visit the summit of Mauna Kea without paying for a private tour, but the challenges are significant. See the "Going on your own" sidebar online with this story at http://www.seattletimes.com/travel.

There are no opportunities to "look through" the telescopes at the summit, and visitors are not allowed at the summit after dark. (Since observatory visiting hours end at 4 p.m., you'll have a long wait to see sunset, if that's a goal.)

The challenge is getting to the top. Only one car-rental firm permits patrons to drive up Mauna Kea: Harper Car and Truck Rental (( http://www.harpershawaii.com/maunakea or 800-852-9993). Based on availability, a one-day rental of a four-wheel drive SUV (required for Mauna Kea) can cost almost as much as the commercial tour rate for one person. (An inquiry in late spring found a rate of $170, another in early fall, $119.)

If you have a four-wheel drive vehicle, you can join a free escorted summit tour, offered 1-4:30 p.m. Saturday and Sunday, from the Mauna Kea Visitor Information Station (Onizuka Center). Tours go into at least one of the Mauna Kea observatories.

There are high-quality telescopes set up at the Onizuka Center, at the mountain's 9,300-foot level, for free, nightly stargazing programs, 6-10 p.m.

While there's no checkpoint to stop you from driving a regular rental car to the summit (and people do), it voids your rental contract, with potentially nasty consequences should you have an accident or breakdown.

You can hike to the summit from the visitor center, a distance of 7 miles with 4,600 feet of elevation gain. Conditions are very challenging, and hikers should allow up to 8 hours for the round-trip. See http://www.ifa.hawaii.edu/info/vis/visiting-mauna-kea/hiking.

TRAVELER'S TIPS:

-There are no stores, restaurants or gas stations on Mauna Kea, and few public restrooms.

-Most Saturday evenings at 6, the Mauna Kea Visitor Information Station hosts free public events, including music nights. The first Saturday of each month, "The Universe Tonight" is a special presentation on the current research and discoveries occurring on Mauna Kea.

-If you drive to the top, start with a full fuel tank; engines use extra fuel on the steep grade and in the thin air.

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MAUNA KEA IS SACRED TO HAWAIIANS

To the outside world, Mauna Kea may be a famous center for astronomy. To native Hawaiians, it is a sacred place ancestors visited for centuries in a quest to understand spiritual connections between earth and the heavens.

To this day, a humble stone and wood lele, or altar, overlooks the observatories from the very summit of Mauna Kea. Continued expansion of the mountain's use by astronomers is a subject of controversy.

In Hawaiian culture, Poliahu, the icy goddess of Mauna Kea, is the antithesis of her fiery archrival, Pele, the goddess of volcanoes. Many say the name Mauna Kea is a shortened version of Mauna a Wakea, meaning "the mountain of Wakea." Wakea is the sky father in the Hawaiian creation story, in which the earth mother gives birth to the island of Hawaii, and this volcanic peak is the child's navel.

To learn more, attend a free presentation at 6 p.m. on the third Saturday of each month when speakers from the community address the mountain from a cultural perspective. It happens at the visitor center of the Onizuka Center for International Astronomy (808-961-2180), on the Mauna Kea summit road.